This application relates to various improvements to an unsymmetrical dynamoelectric machine having an integral multiple of three poles and an integral multiple of three brushes, performing the general function of a motor-generator set in a single integral device, and having capability of accepting or providing power from its rotating shaft. Such a device, known as a Triodyne, is disclosed in U.S. Pat. No. 2,388,023, issued to me on Oct. 30, 1945, and in U.S. Pat. No. Re. 22,907, reissued Aug. 12, 1947, herein incorporated by reference. U.S. Pat. No. Re. 22,907 sets forth the basic theoretical considerations for the design and construction of such a machine.
A device in accordance with the claims of said patents has been constructed, and performed satisfactorily as a voltage controller for electrical welding, with the rotating shaft supporting the load of a ventilating fan. In this application, the device was satisfactory, and provided the low voltage, high current supply needed for welding from a high voltage, low current source. However, in an attempt to use this device as a voltage controller for an electric vehicle, it was found by further analysis and testing that the use of a device according to my previous patents had serious drawbacks. Placing the winding for the main or motor field on a single pole required a large winding, to overcome the reluctance of two air gaps. This large winding in turn requires a large, long pole piece, and a large frame diameter for the device. This would also result in a cooling problem, since the device would approximately double in volume with a less than sixty percent increase in surface area. It was also found that such a dynamoelectric machine would increase in speed upon an attempt to return power from the load, such as for regenerative braking, an undesirable effect in some applications.
Also, with a control pole being fully excited to provide minimum output voltage, and turned off to provide maximum output voltage, the maximum output voltage was further limited by residual magnetism in the control pole, since the resultant residual flux caused something less than full desired output, of an unpredictable and unstable value.
The instant invention overcomes these and other deficiencies of the prior art.